Many versions of three-dimensional memory arrays have been disclosed in the prior art and may be classified as being one of two types: layered and stacked. Layered approaches utilize a technique for bonding two or more memory chips one on top another to form a three-dimensional memory array. There have been variations on this design, such as a design that uses an enhancement comprising heat sink layers that are bonded between memory circuit layers to help reduce overheating.
Of greater interest to the present invention are approaches for manufacturing a layered memory device based on placing diode storage devices at the intersections of the rows and columns within each layer or for manufacturing an electrically programmable read-only memory. Both of these designs involve devices that are manufactured on a semiconductor substrate having decoding logic for the associated bit lines of the memory layers.
All of these designs, however, have shortcomings. The bonding together of multiple chips creates many points of failure and has high associated assembly costs. Manufacturing devices in layers as disclosed in the prior art has the high cost of the base substrate and its electronic circuitry (manufactured using traditional semiconductor manufacturing means) and its associated complexity as well as the many potential points of failure of interconnecting the vast number of row and column bit lines of the various layers.
As advances continue to be made in the area of high density semiconductor storage, the need to keep the cost of these devices low is critical for many applications. Many storage solutions, such as flash memory (a non-volatile, rewritable memory technology), are currently very expensive. As a result, many users of flash memory must upload and download the contents of their memory to other storage means, such as a computer with a hard disk. This is because flash is so expensive that rather than have many flash memory devices, users will typically own very few flash memory devices which they will reuse depending on their current needs. Clearly, a need exists for a low-cost, high-reliability three-dimensional memory device.